Is it possible to have one Discord bot DM another bot?

I'm building out an automated test bot that is meant to test the commands of my main bot. Everything is working fine except that my test bot doesn't seem to be able to receive DMs from the main bot.

I'm currently using discord.js

message.author.send('test dm from one bot to another')

and getting the error:

DiscordAPIError: Cannot send messages to this user

Is there a setting for the bot, or a possible workaround so that I can test my bot's DM functionality?

Both bots can receive DMs from users just fine.